Set up and use feature flags and A/B tests with the Flags SDK (`flags` npm package) and Vercel Flags. Use when installing or configuring the SDK, adding a new or existing flag, wiring `vercelAdapter` (OIDC or SDK keys), declaring flags with `flag()`, using the `vercel flags` CLI (create, inspect, list, enable, disable, set, update, split, rollout, rules, segments, use-targeting, evaluations, versions, open, archive, unarchive, rm, sdk-keys, override, prepare), setting up providers/adapters (Vercel, Statsig, LaunchDarkly, PostHog, GrowthBook, Global Config, OpenFeature, Split, Flagsmith, Reflag, Optimizely, or custom), precompute, `identify`/`dedupe`, Flags Explorer/Toolbar, Next.js or SvelteKit, or encrypting flag values. Triggers: feature flags, feature gates, A/B testing, experimentation, gradual rollout, traffic split, targeting rules, flag overrides, precompute, Flags Explorer, Vercel Flags, vercel flags CLI, `flags/next`, `flags/sveltekit`, `flags/react`, `@flags-sdk/*`.